He knew he would never find the answer. He knew she would never tell him. He knew he would still futilely try and get her to give him the answer. It would never happen but what if she finally relented? Finally allowed him a glimpse of herself, a reason for why everything had happened. He knew she would never give away any part of herself.
The truth was for her a closely guarded secret, one she would never reveal if she revealed it the whole charade would collapse. She would be standing there in a room full of the shards of broken glass. Looking at her life and the wreckage she had caused. Her crown of thorns would be falling.
He wanted this to happen, hope was he had been left with, the hope that she would let slip the truth. The longer she waited, the greater his triumph would be.